Hello, i have a problem with my midi 24 (1 engine Volvo penta B20 6 cil) at low speed the boat has a course problem. There is allright a ruddersafe on the Heckdrive but it is still not working :(
Has any one some tips?
Regards
Maarten Stas
Holland

There are probably many members who know more about this problem but here is a starting comment. It is caused by a phenomenon called "Karman effect". This means that a blunt body moving through a medium such as water or air, sheds vortices alternatively from both sides, thus pulling the stern from starboard to port and back again. When I bought my boat there were no trim tabs and considerable "snaking". After fitting ZIP-wakes there is a considerable but not complete reduction when they are fully extended, which is default at low speeds when in auto mode. If you have conventional trim tabs, try to extend them as much as posible. But whatever you fit to your boat the vortices will still fight it. There are some postings (in swedish) claiming that dual installations fare better than single, but that would be a bit expensive

https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street

Hi Jan, thanks for the info. I have standard trim tabs so I will try that. Regards Maarten